“The clue, Carnes,” said Dr. Bird slowly, “lies in those windows.”

Operative Carnes of the United States Secret Service shook his head before he glanced at the windows of the famous scientist’s private laboratory on the top floor of the Bureau of Standards.

“I usually defer to your knowledge, Doctor,” he said, “but this time I think you are off on the wrong foot. If the thieves came in through the windows, what was their object in cutting that hole through the roof? The marks are very plain and they indicate that the hole was cut in some manner from the inside.”

Dr. Bird smiled enigmatically.

“That is too evident for discussion,” he replied. “I grant you that the thieves entered from the roof through that hole. After they had secured their booty they left by the same route. I presume that you have noticed the marks on the roof where an aircraft of some sort, probably a helicopter, landed and took off. A question of much greater moment is that of what they did before they landed and cut the hole.”

“I don’t follow your reasoning, Doctor.”

“Carnes, that hole was cut through the roof with a heavy saw. In cutting it, the workers dislodged quite a little plaster which fell to the floor and must have made a great deal of noise. Why wasn’t that noise heard?”

“It was heard. The watchman heard it, but knew that Lieutenant Breslau was working here and he thought that he made the noise.”

“Surely, but why didn’t Breslau hear it?”

“How do we know that he didn’t? He was taken to Walter Reed Hospital this morning with his mind an absolute blank and with his tongue paralyzed. He must have seen the thieves and they treated him in some way to ensure his silence. When he is able to talk, if he ever is, he’ll probably give us a good description of them.”

Dr. Bird shook his head.

“Too thin, Carney, old dear,” he said. “Breslau is a very intelligent young man. He was perfectly normal when I left him shortly after midnight last night. He was working alone in here on a device of the utmost military importance. On the desk is a push button which sets ringing a dozen gongs in the building. Surely a man of that type would have had sense enough when he heard and saw intruders cutting a hole through the roof to sound an alarm which would have brought every watchman on the grounds to his assistance. He must have been knocked out before the hole was started, probably before the helicopter’s landing.”

“How? Gas of some sort?”

“The windows were all closed and locked and I have already ascertained that the gas and water lines have not been tampered with. Gas won’t penetrate through a solid roof in sufficient concentration to knock out a man like that. It was something more subtle than gas.”

“What was it?”

“I don’t know yet. The clue to what it was lies, as I told you, in those windows.”

Carnes moved over and surveyed the windows closely.

“I see nothing unusual about them except that they need washing rather badly.”

“They were washed last Friday, but they do look rather dirty, don’t they? Suppose you take a rag and some scouring soap and clean up a pane.”

The detective took the proffered articles and started his task. He wet a pane of glass, rubbed up a thick lather of scouring soap and applied it and rubbed vigorously. With clear water he washed the glass and then gave an exclamation of astonishment and examined it more closely.

“That isn’t dirt, Doctor,” he cried. “The glass seems to be fogged.”

Dr. Bird chuckled.

“So it seems,” he admitted. “Now look at the rest of the glass around the laboratory.”

Carnes looked around and then walked to a table littered with apparatus and examined a dozen pieces carefully.

“It’s all fogged in exactly the same way, Doctor,” he said. “The only piece of clear glass in the room is that piece of plate glass on your desk.”

Dr. Bird picked up a hammer and struck the plate on his desk a sharp blow. Carnes ducked instinctively, but the hammer rebounded harmlessly from the plate.

“That isn’t glass, Carnes,” said the doctor. “That plate is made of vitrilene, a new product which I have developed. It looks like glass, but it has entirely different properties. It is of enormous strength and is quite insensitive to shock. It has one most peculiar property. While ultra-violet and longer rays will penetrate it quite readily, it is a perfect screen for X-rays and other rays of shorter wave length. It appears to be the only piece of transparent substance in my laboratory which has not been fogged, as you call it.”

“Do short waves fog glass, Doctor?”

“Not so far as I know at present, but you must remember that very little work has been done with the short wave-lengths. In the vast range of waves whose lengths lie between zero and that of the X-ray, only a few points have been investigated and definitely plotted. There may be in that range a wave-length which will fog glass.”

“Then your theory is that some sort of a ray machine was put in operation before the helicopter landed?”

“It is too early to attempt any theorizing, Carnes. Let us confine ourselves to the known facts. Lieutenant Breslau was normal at midnight and was working in this room. Some time between then and seven this morning he underwent certain mental and physical changes which prevent him from telling us what he observed. During the same period, a hole was cut in the roof and things of great importance stolen. At the same time, all the glass in the laboratory became semi-opaque. The problem is to determine what connection there is between the three events. I will handle the scientific end here, but there is some outside work to be done, and that will be your share.”

“Give your orders, Doctor,” said the detective briefly.

“To understand what I am driving at, I will have to tell you what has been stolen. Naturally this is highly confidential. Some rumors have leaked out as to my experiments with ‘radite, ‘ as I have named the new radium-containing disintegrating explosive on which I have been working, but no one short of the Secretary of War and the Chief of Ordnance and certain of their selected subordinates knows that my experiments have been successful and that the United States is in a position to manufacture radite in almost unlimited quantities from the pitchblende ore deposits of Wyoming and Nevada. The effects of radite will be catastrophic on the unfortunate victim on whom it is first used. The only thing left to do was to develop a gun from which radite shells could be fired with safety and precision.

“Ordinary propellant powders are too variable for this purpose, but I found that radite B, one form of my new explosive, can be used for propelling the shells from a gun. The ordinary gun will last only two or three rounds, due to the erosive action of the radite charge on the barrel, and ordinary ordnance is heavier and more cumbersome than is necessary. When this was found to be the case, the Chief of Ordnance detailed Lieutenant Breslau, the army’s greatest expert on gun design, to work with me in an attempt to develop a suitable weapon. Breslau is a wizard at that sort of work and he has made a miniature working model of a gun with a vitrilene-lined barrel which is capable of being fired with a miniature shell. The gun will stand up under the repeated firing of radite charges and is very light and compact and gives an accuracy of fire control heretofore deemed impossible. From this he planned to construct a larger weapon which would fire a shell containing an explosive charge of two and one-half ounces of radite at a rate of fire of two hundred shots per minute. The destructive effect of each shell will be greater than that of the ordinary high-explosive shell fired from a sixteen-inch mortar, and all of the shells can be landed inside a two-hundred foot circle at a range of fifteen miles. The weight of the completed gun will be less than half a ton, exclusive of the firing platform. It is Breslau’s working model which has been stolen.”

Carnes whistled softly between his teeth.

“The matter will have to be handled pretty delicately to avoid international complications,” he said. “It’s hard to tell just where to look. There are a great many nations who would give any amount for a model of such a weapon.”

“The matter must be handled delicately and also in absolute secrecy, Carnes. We are not yet ready to announce to the world the fact that we have such a weapon in our armory. It is the plan of the President to have a half dozen of these weapons manufactured and give a demonstration of their terrible effectiveness to representatives of the powers of the world. Think what an argument the existence of such a weapon will be for the furtherance of his plans for disarmament and universal peace! Public sentiment will force disarmament on the world, for even the worst jingoist could no longer defend armaments in the face of America’s offer to scrap these super-engines of destruction and to destroy the plans from which they were made. If the model has fallen into the hands of any civilized power the damage is not irreparable, for public opinion would force its surrender and return. It is among the uncivilized powers that our search must first be made.”

“That makes the problem of where to start more complicated.”

“On the contrary, it simplifies it immensely. At the head of the uncivilized powers stands one which has the brains, the scientific knowledge and the manufacturing facilities to make terrible use of such a weapon. In addition, the aim of that power is to overthrow all world governments and set up in their stead its own tyrannical disorder. Need I name it?”

“You refer to Russia.”

“Not to Russia, the great slumbering giant who will some day take her place in the sun in fellowship with the other nations, but to Bolsheviki, that empire within an empire, that horrible power which is holding sleeping Russia in chains of steel and blood. It is there that our search must first be made.”

“Of course, they have no official representative in America.”

“No, but the Young Labor Party is as much their accredited representative as the British Ambassador is of imperial Britain. Your first task will be to trail down and locate every leader of that group and to investigate his present activities.”

“I can tell you where most of them are without investigation. Denberg, Semensky and Karuska are in Atlanta; Fedorovitch and Caspar are in Leavenworth; Saranoff is dead--”

“Presumably.”

“Why, Doctor, I saw with my own eyes the destruction of the submarine in which he was riding!”

“Did you see his dead body?”

“No.”

“Neither did I, and I will never be sure until I do. Once before we were certain of his death, and he bobbed up with a new fiendish device. We cannot eliminate Saranoff.”

“I will include him in my plans.”

“Do so. Besides a hypothetical Saranoff, there are a half dozen or more of the old leaders of the gang who are alive and at liberty, so far as we know. They fled the country after the Coast Guard broke up their alien smuggling scheme, but some of them may have returned. There are also thirty or forty underlings who should be located and checked up on, and, in addition, we must not lose sight of the fact that new heads of the organization may have been smuggled into the United States. It is no simple task that I am setting you, Carnes, but I know that you and Bolton will see it through if anyone can.”

“Thanks, Doctor, we’ll do our best. If I am not speaking out of turn, what are you planning to do in the mean time?”

“I am going to start Taylor off on an ultra-short wave generator and try a few experiments along that line. Breslau is at Walter Reed and they are doing all they can for him, but until I can get some definite information as to the underlying cause of his condition, they are more or less shooting in the dark.”

“How are they treating him?”

“By electric stimulations and vibratory treatments and by keeping him in a darkened room. By the way, Carnes, if I am correct in my line of thought, it would be well to have an extra guard put over Karuska. He was the only real expert in ordnance that the Young Labor party had, and if they have Breslau’s model they’ll need him to supervise the construction of a gun.”

“I’ll attend to that at once, Doctor. Is there anything else?”

“Not that I know of. I am going out to Takoma Park this afternoon and have another look at Breslau, but it is too soon to hope for any change in his condition. Aside from the time I will be out there, you can find me either here or at my home, in case anything develops.”

“I’ll get on the job at once, Doctor.”

“Thanks, old dear. Remember that speed must be the keynote of your work.”

The telephone bell at the head of Dr. Bird’s bed woke into noisy activity. The doctor roused himself and took down the instrument sleepily. A glance at the clock showed him that it was four in the morning and he muttered a malediction on the one who had called him.

“Hello,” he said into the receiver. “Dr. Bird speaking.”

“Doctor,” came a crisp voice over the wire, “wake up! This is Carnes talking. Something has broken loose!”

All trace of sleep vanished from Dr. Bird’s face and his eyes glowed momentarily with a peculiar glitter which Carnes would at once have recognized as indicative of the keenest interest.

“What has happened, Carnes?” he demanded.

“I telephoned Atlanta this morning and arranged to have an extra guard put over Karuska as you suggested. The matter was simplified by the fact that he and nine others were confined in the prison infirmary. The warden agreed to do as I told him, and, in addition to the regular guards, a special man was placed in the ward near Karuska’s bed. At 2 A. M. the lights in the ward went out.”

“Accidentally, or were they put out?”

“They haven’t found out yet. At any rate they are all right now, but Karuska and all of the other inmates and all the guards of that particular ward have gone crazy.”

“The dickens you say!”

“Not only that, they are also partially paralyzed. The description I got over the telephone corresponds exactly with the condition of Lieutenant Breslau as you described it to me. Here is the most interesting part of the whole affair. The special guard over Karuska was only lightly affected and has already recovered and is in a position to tell you exactly what happened. I got a garbled account of the affair from the warden, something about a goldfish bowl or something like that, the warden wouldn’t take it seriously enough to give me details. I didn’t press for them much for I knew that you would rather get them at first hand.”

“I certainly would. I’ll be ready to leave for Atlanta in less than ten minutes.”

“I expected that, Doctor, and a car is already on its way to pick you up. I’ll meet you at Langley Field where a plane is already being tuned up and will be ready to take off by the time we get there.”

“Good work, Carnes. I’ll see you at the field.”

A car was waiting for Carnes and Dr. Bird when the Langley Field plane slid down to a landing at Atlanta. At the penitentiary, Dr. Bird went direct to the infirmary where Karuska had been confined. As he entered, he shot a keen glance around and gave an exclamation of satisfaction.

“Look at the windows, Carnes,” he cried.

Carnes went over to the nearest window and moistened his finger tip and applied it experimentally to the glass. The moisture produced no effect, for the glass of the windows was permanently clouded as was that of the doctor’s laboratory.

“Whatever happened in my laboratory the night before last was repeated here last night with a similar object,” said the doctor. “The object there was to steal a gun model; here it was to steal a man who could construct a full-sized gun from the model. I understand that one of the guards escaped the fate which overtook the rest of the persons in the infirmary?”

“Not altogether, Doctor,” replied the warden. “I think that his mind is somewhat affected, for he tells a wild yarn and insists on trying to wear a goldfish bowl on his head. I have him under observation in the psychopathic ward.”

Dr. Bird shot a scornful glance at the warden.

“‘There are none so blind as those who will not see’,” he murmured.

“By all means, I wish to see him,” he went on aloud. “Will you have him brought here at once, please?”

The warden nodded and spoke to one of the attendants. In a few moments a tall, fair-haired young giant stood before the doctor. Dr. Bird pushed back his unruly shock of black hair with his fingers, those long slim mobile fingers which alone betrayed the artist in his make-up, and shot a piercing glance from his black eyes into the blue ones, which returned the gaze unabashed.

“What is your name?” he asked.

“Bailley, sir.”

“You were on guard here last night?”

“Yes, sir. I was detailed as a special guard over No. 9764.”

“Tell me in your own words just what happened. Don’t be afraid to speak out; I’m not going to disbelieve you; and above all, tell me everything, no matter how unimportant it may seem to you. I’ll judge the importance of things for myself. I’m Dr. Bird of the Bureau of Standards.”

The guard’s face lighted up at the doctor’s words.

“I’ve heard of you, Doctor,” he said in a relieved tone, “and I’ll be glad to tell you everything. At ten o’clock last night, I relieved Carragher as special guard over No. 9764. Carragher reported that the prisoner was somewhat restless and hadn’t been asleep as yet. I sat down about fifteen feet from his bed and prepared to keep an eye on him until I was relieved at six o’clock this morning.

“Nothing happened until about two o’clock. No. 9764 was restless as Carragher had said, but toward midnight he quieted down and apparently went to sleep. I was sleepy myself, and I got up and took a turn around the room every five minutes to be sure that I kept awake. That’s how I am so sure of the time, sir.”

Dr. Bird nodded.

“At five minutes to two, just as I got up, I heard a noise outside like a big electric fan. It sounded like it came from directly overhead and I went to the window and looked out. I couldn’t see anything, although I could hear it pretty plainly, and then I heard a noise like something had fallen on the roof. Almost at the same time there came a sort of high-pitched whine, a good deal like the noise an electric motor makes when it is running at high speed.

“I thought of giving an alarm, but I didn’t want to stir things up unless I was sure that there was some necessity for it, so I started for the door to ask one of the outside guards if he had heard anything. As I turned toward No. 9764 I saw that he had been sitting up in bed while my back was turned. As soon as he saw that I noticed him, he lay back real quick and pulled the covers over his head. He moved pretty quick, but not so quick that I couldn’t see that he had something that glittered like glass before his face. I started over toward his bed to see what he was doing and then it was that the lights started to get dim!”

“Go on!” said the doctor as Bailley paused. His eyes were glittering brightly now.

“Well, sir, Doctor, I don’t hardly know how to describe what happened next. The lights were getting dim, but not as they ordinarily do when the current starts to go off. The filaments were shining as bright as they ever did, but the light didn’t seem to be able to penetrate the air. The whole room seemed to be filled with a blackness that stopped the light. No, sir, it wasn’t like fog; it was more like something more powerful than the lights was in the room and was killing them.

“It wasn’t only the lights which were affected, it was me as well. This blackness, whatever it was, was getting into me as well as into the room, and I couldn’t seem to make myself think like I wanted to. I tried to yell to give an alarm, and I found that I could hardly whisper. I went toward the bed and then I saw No. 9764 sit up again. He had a goldfish bowl pulled down over his head and it was evident that it was keeping the blackness away, for I could see him plainly and his eyes were as bright as ever.

“The nearer I got to him, the funnier I felt, and I began to be afraid that I would go out. No. 9764 got up out of bed, and I could see him grinning at me through the bowl. He reached up and adjusted that bowl, and all of a sudden I realized that whatever was knocking me out was not affecting him because he had that thing on. I jumped for him with the idea of taking the bowl off and putting it on my own head. He saw what I was up to and he fought like a cornered rat, but the blackness hadn’t affected my muscles. I’m a pretty big man, sir, and No. 9764 is a little runt, and it didn’t take me long to get the bowl off his head and pulled on over mine. As soon as I did that, I seemed to be able to think clearer. I was sitting on No. 9764 and was ready to tap him with a persuader if he started anything, but I didn’t have to. In a few minutes he stopped struggling and lay perfectly quiet.

“The lights kept getting dimmer and dimmer until they went out altogether and the room became pitch dark. It wasn’t exactly as if the lights had gone out, sir; I seemed to know that they were still there and were burning as bright as ever, but they couldn’t penetrate the blackness in the room, if you understand what I mean.”

“I think I do,” said Dr. Bird slowly. “It was a good deal as if you had seen a glass filled with a pale red liquid and someone had dumped black ink into the fluid and hid the red color. You would know that the red was still there, but you wouldn’t be able to see it through the black.”

“That’s exactly what it was like, Doctor; you have described it better than I can. At any rate, after it got real dark I heard a low whistle from the roof. No. 9764 made a struggle to get up for a moment and then lay quiet again. The whistle sounded again and then I heard some one call ‘Caruso.’ Everything was quiet for a while and then the same voice called again and said some stuff in a foreign language that I couldn’t understand. I kept perfectly quiet to see what would happen.

“For about ten minutes the room remained perfectly dark, as I have said, and all the while I could hear that whining noise. All of a sudden it began to sound in a lower note and then I could see the lights again, very dimly and like the black ink you spoke of was fading out. The note got lower until it stopped altogether, and the lights came on brighter until they were normal again. Then I heard a scraping noise on the roof and the noise I had heard at first like a big electric fan. I looked at the clock. It was two-twenty.

“For a few minutes I wasn’t able to collect my wits. When I got up off of No. 9764 at last he stared at me as though he didn’t know a thing, and I heaved him back into his bed and ran to the door to summon an outside guard. I could still talk in a husky whisper, but not loud, and I wasn’t surprised when no one heard me. My orders were not to let No. 9764 out of my sight, but this was an emergency, so I left the ward and found a guard. It was Madigan and he was standing on his beat staring at nothing. When I touched him he looked at me and there was the same vacant look in his eyes that I had seen in the prisoner’s. I talked to him in a whisper, but he didn’t seem to understand, so I left him and went to a telephone and called for help. Mr. Lawson, the warden, got here with guards in a couple of minutes and I tried to tell him what had happened, but I couldn’t talk loud, and I was afraid to take the fish bowl off my head.”

“What happened next?”

“Mr. Lawson took me to his office, and on the way we passed under an arc light. As soon as I got under it I begin to feel better, and my voice came stronger. I saw that it was doing me some good and I stopped under it for an hour before my voice got back to normal. It seemed to clear the fog from my brain, too, and I was able, about four o’clock, to tell everything that had happened. Mr. Lawson seemed to think that my brain was affected as well as the others’ and he sent me to the hospital. That’s all, Doctor.”

“Do you feel perfectly normal now?”

“Yes, sir.”

“There is no need for confining this man longer, Mr. Lawson. He is as well as he ever was. Carnes, get the Walter Reed Hospital on the telephone and tell them that I said to treat Lieutenant Breslau with light rays, rich in ultra-violet. Tell them to give him an overdose of them and not to put goggles on him. Keep him in the sun all day and under sun-ray arcs at night until further orders. Mr. Lawson, give the same treatment to the men who were disabled last night. If you haven’t enough sun-ray arcs in your hospital, put them under an ordinary arc light in the yard. Bailley, have you still got that goldfish bowl?”

“It is in my office, Doctor,” said the warden.

“Good enough! Send for it at once. By the way, you have two more communists here, Denberg and Semensky, haven’t you?”

“I think so, although I will have to consult the records before I can be positive.”

“I am sure that you have. Look the matter up and let me know.”

The warden hurried away to carry out the doctor’s orders, and an orderly appeared in a few moments with a hollow globe made of some crystalline transparent substance. Despite its presence in the infirmary the evening before, there was no trace of clouding apparent. Dr. Bird took it and examined it critically. He rapped it with his knuckles and then stepped to the door and hurled it violently down on the concrete floor of the yard. The globe rebounded without injury and he caught it.

“Vitrilene, or a good imitation of it,” he remarked to Carnes. “After you get through talking to the hospital, get Taylor on the wire. There is plenty of loose vitrilene in the Bureau, and I want him to send down about fifty square feet of it by a special plane at once.”

As Carnes left the room, the warden reappeared.

“The men are all lying in the sun now, Doctor,” he said. “I find that we have the two men you mentioned confined here. They are both in Tier A, Building 6.”

“Is that an isolated building?”

“No, it is one wing of the old main building.”

“On which floor?”

“The second floor. It is a six-story building.”

“Have they been moved there recently?”

“They have been there for nearly a year.”

“In that case there will be little chance of another attack of this sort to-night. At the same time, I would advise you to station extra guards there to-night and every night until I notify you otherwise. Caution them to watch the lights carefully and to give an alarm at once if they appear to get dim. In such a case, send men to the roof with rifles with orders to shoot to kill anyone they find there. I am going back to Washington and I am going to take Karuska, your No. 9764 with me. You had better have one of the guards in the corridor, where Denberg and Semensky are, wear this goldfish bowl, as you call it. A lot of plate glass--at least it will look like that--will come from Washington by plane. Cut it into sheets a foot square and use surgeon’s plaster to make some temporary glass helmets for your men. I want all your guards to wear them until I either settle this matter or else send you some better helmets. Do you understand?”

“I understand all right, but I’m afraid that I can’t do it. The wearing of such appliances would interfere with the efficiency of my men as guards.”

“Brain and tongue paralysis would interfere rather more seriously, it seems to me. In any event, I have sufficient authority to enforce my request. If you are at all doubtful, call up the Attorney General and ask him.”

The warden hesitated.

“If you don’t mind, I think I will call Washington, Doctor,” he said. “I will have to get authority to turn No. 9764 over to you in any event.”

“Call all you wish, Mr. Lawson. Mr. Carnes is talking to Washington now and we’ll have a clear line through for you in a few minutes. Meanwhile, get a set of shackles on Karuska and get him ready to travel by plane. He appears to be suffering from mental paralysis, but I don’t know how his case will develop. He may go violently insane at any moment and I don’t care to be aloft in a plane with an unbound maniac.”

Major Martin looked up from the prone figure of Karuska.

“His condition duplicates that of Lieutenant Breslau, Dr. Bird,” he said. “We received your telephoned message this afternoon and we kept Breslau in a flood of sunlight until dusk, and then put him under sun-ray lamps. I don’t know how you got on to that treatment, but it is having a very beneficial effect. He can already make inarticulate sounds, and his eyes are not quite as vacant at they were. If he keeps on improving as he has, he should be able to talk intelligently in a few days. If you wish to question this man, why not give him the same treatment?”

“I haven’t time, Major. I must make him talk to-night if it is humanly possible. I called you in because you are the most eminent authority on the brain in the government service. Is there any way of artificially stimulating this man’s brain so that we can force the secrets of his subconscious mind from him?”